The present invention relates in general to an apparatus and method for obtaining test core samples and in particular to an apparatus and method for obtaining test core samples from pavement.
In the paving industry, State Dept. of Transportation, County, City and Federal Aviation Administration Officials, Authorities and Engineers as well as the above from the private sector of the construction industry, require that paving contractors of their representatives drill out core samples of the pavement within certain time constraints, or at a later time for investigative and informational purposes. These cores are subjected to various tests to verify different properties and density. The core samples are generally obtained by using a vertical core drill which drills out a core of the pavement using a tubular diamond-tipped bit driven by a gas or electric drilling machine. The cores will generally vary in length and are of varying diameters, depending on the agency specifications and/or preference of the testers.
To test the cores and obtain results that are representative in general, it is important to obtain the cores in a timely and cost effective manner. Several methods presently used to obtain core samples are: 1) Drilling a second identical core next to the sample core hole, chipping out the second core hole and then getting under the sample core with a lever and prying it out. 2) Driving a pair of rods through the surrounding material and prying out the core. 3) Digging a wedge shaped hole next to the core and prying it out. 4) Drilling through the entire depth of the pavement and extracting the core from the hole using an apparatus for pulling cores such as that described in the Richardson, Jr. Patent (U.S. Pat. No. 5,431,466), which represents the present state of the art. These methods are time consuming, hence labor costly and materials (core bit) costly, due to having to drill (in many instances) the depth of the full pavement, when only a small portion of the top surface may be tested.
With the specifying agencies continuously requiring a better product and more quality control, the number of cores to be drilled and tested has increased. The problem of obtaining test cores in a timely and cost effective manner has increased over the past years. This is particularly true where the pavement to be tested is a surface layer of asphalt (2 inches is common) underlaid with 8 inches of concrete (common on large expressways). Drilling a core through the full depth of pavement under these circumstances can take 45 minutes or longer and may wear out a single 4 inch diamond tipped core bit at an average cost of $300 or more. This is an extremely inefficient use of time and materials when it is common that only the top 2 inches of asphalt is required for examination. This top layer of asphalt can be drilled in substantially less time than drilling the full depth of pavement (approximately 2 minutes or less), especially when drilling a full core requires drilling through concrete. Drilling only the top layer also saves dramatically on equipment, where a single core bit may last through several hundred cores of the top layer of asphalt. What is needed is a tool that can efficiently and easily break off and extract cores from pavement surfaces without the necessity of drilling the depth of full pavement.
It is an object of the present invention to provide an apparatus and method for obtaining undamaged test cores which only requires drilling to a specified depth in the top surface, and does not require drilling the full depth of pavement.
It is another object of the invention to provide an apparatus and method for obtaining test cores in a timely and cost effective manner.
It is a further object of invention to provide an apparatus and method of obtaining test cores which can be used with industry standard drill bits for taking core samples from the pavement.
These and other objects and advantages of the present invention are realized in one embodiment of an apparatus for breaking off cores, comprising a split tube, a handle attached to the top of the split tube, and tightening device for moving confronting ends of the split tube towards each other and away from each other if desired, the tightening device being located on the middle portion of the split tube.
The method of the present invention includes the steps of providing an apparatus for the breaking off of cores, inserting the apparatus to a predetermined depth in a space that has been drilled around a core with industry standard drill bits, tightening the apparatus and using lateral force to break off the core.